Author Topic: SpaceX Crewed Dragon: Pressing home the advantage  (Read 219357 times)

Offline douglas100

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #40 on: 01/10/2013 09:58 pm »
Unsure if they need a functional 2nd stage on the test. They could do it like the Apollo program, just a 1st stage. Or just put some weight to simulate the 2nd stage.

And I think SpaceX will try to persuade NASA to do a 1st stage recovery some seconds after the LAS test. Depends on how fast Grasshopper evolves.

Attempting recovery (even if they were ready to do it on this flight) would be a bad idea. It's absolutely vital that this test is successful if the manned Dragon is to go ahead. It would be stupid to risk this by have an extra test objective.
Douglas Clark

Offline Robotbeat

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #41 on: 01/10/2013 10:07 pm »
Could they combine the in-flight abort test with a test of the F9 first stage's ability to propulsively land? I.e. Dragon "punches off" of the F9 and lands, meanwhile the F9 also tests its boost-back and propulsive landing?
I seriously doubt they'd do it.
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Offline oiorionsbelt

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #42 on: 01/10/2013 10:09 pm »

Attempting recovery (even if they were ready to do it on this flight) would be a bad idea. It's absolutely vital that this test is successful if the manned Dragon is to go ahead. It would be stupid to risk this by have an extra test objective.
Really? Even if the first stage has propelled the Dragon to the required altitude and velocity, separated and has nothing else to do for the abort test?

Offline StephenB

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #43 on: 01/10/2013 10:13 pm »
Just curious about how environmental impact factors into all of this. The most likely scenario is that a mostly fully fueled 1st stage and a fully fueled second stage crash into the Atlantic, right? LOX wouldn't be a concern, but what about all the RP-1?

Offline Lurker Steve

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #44 on: 01/10/2013 10:26 pm »
Could they combine the in-flight abort test with a test of the F9 first stage's ability to propulsively land? I.e. Dragon "punches off" of the F9 and lands, meanwhile the F9 also tests its boost-back and propulsive landing?

If they wait for F9R to be ready before performing their abort tests, they won't complete their milestones and get certified before 2017.

Offline hrissan

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #45 on: 01/10/2013 10:31 pm »
Can't see that as even being possible. Thrust termination occurs prior to or simultaneous with LAS motor ignition and capsule separation.
But LAS should be able to save capsule from accelerating rocket (10g versus 3g), so may be the test will not attempt to shut down first stage engines at all?

If the stack survives shock, it could continue climbing until second stage separation and then attempt first stage recovery?

Also may be it is possible to use more sturdy mass simulator instead of complete second stage?

Offline Karloss12

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #46 on: 01/10/2013 10:33 pm »
Instead of shutting down all Merlins could they just throttle the centre engine to minimum while the Dragon clears the core and then recover the 1st stage.  I expect it will involve a bit of persuading NASA that it won't affect the certification of the Dragon LAS.

Why would you want to do this? It just increases the risk that the booster rams into the capsule, which is a test failure.

As the 1st stage wouldn't be reaching its intended altitude and speed, would the 1st stage have to launch half empty as it wouldn't have enough time to expend the fuel through the centre engine in time?

Can F9 launch on half a tank?

Sure, but again, what's the point of testing if you're going to perform the test in conditions that are guaranteed NOT to match an actual abort?

For your first question:
If the Dragon LAS provides anywhere near the acceleration of the Blue origins LAS (check out the video) then I don't think the centre merlin engine throttled down to minimum thrust has any risk of causing the booster to bump into the bottom of the dragon.  In any case this tiny bit of thrust wouldn't void the test, it just makes it that tiny bit more difficult.  I don't think NASA would be able to argue if SpaceX volunteers to make the test more difficult.  If during the analysis of the static launch abort test SpaceX calculates that there is plenty of margin to leave the centre merlin engine on minimum thrust then SpaceX potentially recovers the stage and therefore saves ~$30mil.  So the answer to your first question is 'money'.

For the second question:
As long as SpaceX do their sums correctly and a half full F9 is launched on a profile that at the moment the Launch Abort occurs the F9 has the same MaxQ, acceleration, velocity, altitude etc of a regular F9 launch, than that is all that matters for the LAS test.  Before the launch abort initiates the launch profile can be what ever it wants.

Offline oiorionsbelt

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #47 on: 01/10/2013 10:34 pm »
Could they combine the in-flight abort test with a test of the F9 first stage's ability to propulsively land? I.e. Dragon "punches off" of the F9 and lands, meanwhile the F9 also tests its boost-back and propulsive landing?
What about say just an engine restart or perhaps simply reorienting the stage. ISTM there are a lot of things that could be "added" to the in flight abort test that would not interfere wit the the primary objective .

Offline douglas100

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #48 on: 01/10/2013 10:36 pm »

Attempting recovery (even if they were ready to do it on this flight) would be a bad idea. It's absolutely vital that this test is successful if the manned Dragon is to go ahead. It would be stupid to risk this by have an extra test objective.
Really? Even if the first stage has propelled the Dragon to the required altitude and velocity, separated and has nothing else to do for the abort test?

Yes, really. I think the first stage will be shut down before the Dragon separates. But after the Dragon separates at maxQ I think there is a very good chance the vehicle will break up due to aerodynamic forces. It's quite possible that after separation the RSO may press the Big Red Button. This isn't a waste: if the test is a success, SpaceX get paid.

Re-usability isn't the top priority. Fulfilling the manifest and getting the manned Dragon operational are more important. SpaceX will have plenty of opportunities on other flights, where the first stage follows a nominal trajectory, to test their recovery technologies.
Douglas Clark

Offline oiorionsbelt

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #49 on: 01/10/2013 10:47 pm »
Agreed that re-uasability isn't the main objective of an in flight abort test and perhaps you're right the vehicle will be destroyed by the RSO but if it is not a danger to others and does not break up, it could have a useful purpose before crashing into the Atlantic.

Offline Comga

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #50 on: 01/10/2013 11:02 pm »
Agreed that re-uasability isn't the main objective of an in flight abort test and perhaps you're right the vehicle will be destroyed by the RSO but if it is not a danger to others and does not break up, it could have a useful purpose before crashing into the Atlantic.

Yes, like demonstrating the RSO's "Big Red Button".

KISS!

Remember that one of the big issues for Ares-1 was that the Orion parachutes were not assured of surviving the environment anticipated after the destruction of the first stage?
A full up test has to be full up.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline go4mars

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #51 on: 01/10/2013 11:09 pm »
I doubt that any payload atop the second stage nestled inside the trunk barrel would survive a transonic abort because of the dynamic pressure. Air would rush into the trunk barrel after the capsule separates and almost certainly destroy any satellite residing there.
Maybe they could fix that with a pica-x covered lid. 

As for first stage RTLS, the transonic abort would occur at a significantly lower altitude than upper stage separation on the nominal flight trajectory. I doubt that the first stage structure would survive the flip to retrograde at that altitude. They need to get the first stage up and out of the sensible atmosphere to do the boost-back maneuver. And they can't just keep burning the stage because they need to demonstrate first stage shutdown as part of the abort demonstration.
Maybe it would be a good opportunity to demonstrate 9-engine re-start.  Isn't the merlin 1D supposed to be able to do that?  Yes there would likely be several seconds of gravity losses.

Can F9 launch on half a tank?
Interesting question.  Perhaps grasshopper suggests yes. 

It would be stupid to risk this by have an extra test objective.
If it saves or makes money and has a benefit, it's worth looking into.  It's a business.

environmental impact factors...fueled second stage crash into the Atlantic,...what about all the RP-1?
Total non-issue.  You'd feed a few microbes that live in the ocean.  The natural seepage rate of crude oil into the ocean is so much larger than this, ...  Well, let's just say it's a very short-term, extremely small concern.  RP-1 isn't crude, and they aren't launching the Exxon Valdez.  In addition, nearly all of it would burn on the way down after the flight termination system unzipped the tanks.
« Last Edit: 01/10/2013 11:12 pm by go4mars »
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline sanman

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Offline Ronsmytheiii

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #53 on: 01/10/2013 11:27 pm »
Quote
The actual pad abort test itself will take place in December, resulting in a full-up Falcon 9 and Dragon being integrated on the Cape Canaveral launch site, prior to aborting the Dragon from the pad for a full test.

This seems strange. Why demonstrate pad abort off of an otherwise perfectly good Falcon? Haven't all previous pad abort demos been done from the ground, there-by not risking damage to flight / GSE hardware?

Going over the video again, the big G never said that Dragon would be on a Falcon 9 for the pad abort, only that Dragon would be close to the final design and would demonstrate the abort capability off LC-40, they might just fire the Capsule itself off the pad.

Offline notsorandom

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #54 on: 01/10/2013 11:33 pm »
Agreed that re-uasability isn't the main objective of an in flight abort test and perhaps you're right the vehicle will be destroyed by the RSO but if it is not a danger to others and does not break up, it could have a useful purpose before crashing into the Atlantic.

Yes, like demonstrating the RSO's "Big Red Button".

KISS!

Remember that one of the big issues for Ares-1 was that the Orion parachutes were not assured of surviving the environment anticipated after the destruction of the first stage?
A full up test has to be full up.
Agreed, the best test would be the most realistic. I would bet that the Falcon 9 is going to have a role to play in the abort tests too. It has to do things during an abort too. It will be transmitting telemetry. Presumably it would try and shut its engines down. It will also be transmitting telemetry while the abort is happening. If there is something odd or unexpected in the behavior of the Falcon or Dragon that engineering data would be priceless. It may also be a good idea for them to have the RSO "unzip" the rocket and see what kind of environment that subjects the Dragon to. 

Offline Rocket Science

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #55 on: 01/10/2013 11:56 pm »
Nice article Chris! :) I look forward to the next in the series...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Zed_Noir

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #56 on: 01/11/2013 12:16 am »
I am confuse. Are we talking about the 2013 Dragon pad abort test or the 2014 in-flight Dragon abort test?

Offline oiorionsbelt

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #57 on: 01/11/2013 12:25 am »
Both I believe

Offline Dappa

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #58 on: 01/11/2013 12:29 am »
Going over the video again, the big G never said that Dragon would be on a Falcon 9 for the pad abort, only that Dragon would be close to the final design and would demonstrate the abort capability off LC-40, they might just fire the Capsule itself off the pad.
SpaceX might as well launch the Pad Abort test from a F9, the one they plan to use for the Ascent Abort test a few months later. This way, they don't have to design and build a test stand specifically for the abort test.

On top of that, I speculate that this is not just a test of the Dragon, but one of a system. This could include rescue of the 'crew', safing of the launch vehicle, confirm software interaction between vehicles, and who knows what else. I think it'll be interesting to find out what they'll the plan is.

Offline go4mars

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Re: SpaceX Crewed Dragon: Pressing home the advantage
« Reply #59 on: 01/11/2013 12:38 am »

Maybe these are related thoughts too:

environmental impact factors...fueled second stage crash into the Atlantic,...what about all the RP-1?


...opportunity to demonstrate 9-engine re-start.  Isn't the merlin 1D supposed to be able to do that?
« Last Edit: 01/11/2013 12:39 am by go4mars »
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

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